With one-piece rims, known runflat devices are generally constituted by a support ring which is clamped around a wheel rim inside a tire. That ring is formed either as a single piece with relatively flexible sides which may be continuous, or it may be a split flexible piece (i.e. from which a slice has been removed), or it may be formed from at least two rigid pieces each in the form of a circular arc or sector.
In the past, in order to mount the split ring or ring sectors in a clamped configuration around the rim, a rigid assembly and clamping fastener was used between the two free ends of the split ring or between the facing ends of the ring sectors, for example a fastener of the nut-and-bolt type. However, experience has shown that such fasteners can constitute the weak link in runflat devices (fatigue phenomena, for example).
The Assignee's European patent document EP-A-1 153 769 proposes a runflat device that can overcome the problems caused by such assembly and clamping fasteners. That device comprises a support ring for mounting on an asymmetrical one-piece type wheel rim having a drop center and an axially inner rim flange and an axially out rim flange, said ring being produced in at least two independent sectors, each having radially inner and outer zones, and is such that each sector is fixed to the rim at its radially inner zone using a screw or a clamping belt which surrounds the outer lateral flanges of the ring sectors. More precisely, the radially inner zone of each ring sector terminates in an arcuate sole which is designed to bear against the bottom of the drop center and which is formed by two lateral flanges, an inner flange and an outer flange, the inner flange being received in a lateral groove defined by the drop center while the outer flange, which matches the profile of the drop center, cooperates with means for fixing the ring sector on the rim.